1. Field of the Invention
The invention relates to a bone nail bent at least in its proximal end portion and consisting of elastic material of round or oval cross section for fixing fractures in the proximal femural area, comprising at least one bone nail of resilient material, which nail is insertable into a medullary canal of a bone through an impact hole formed in the bone proximal to the knee joint area and which abuts under tension with its apex of curvature the wall of the medullary canal opposing the impact hole due to its elasticity, whose portion adjacent the distal end of the bone nail has the same cross section as the entire nail, and which is provided for forming as a coupling element for the production of a non-rotatable connection to a tool with a flattening in at least one site of the nail circumference at a distance from the distal nail end. The invention further relates to a tool for the connection to the distal end area of such a bone nail.
2. Discussion of the Prior Art
It is known to reposite and to fix pertrochanterous and subtrochanterous fractures by opening the medullary canal of the bone through an impact hole and by introducing into this impact hole at least one bone nail, conveniently several bone nails consisting of elastic material and being bent at least in its (their) proximal area. When introducing such bone nails into the medullary canal, the nails, under tension due to their elasticity, abut the wall of the medullary canal opposing the impact hole with their apex of curvature, so that on the proximal point of each nail arriving at the site of the fracture, the nail passes beyond this fracture into the condyle of the bone and fixes the fracture. By rotating the individual nails, the bone portions can be reduced so that they assume the correct relative position at the site of the fracture. For this purpose, the distal end of each nail is provided with a coupling member allowing a wholly non-rotatable connection with an impact tool.
It is known to give this coupling member the form of a hook-shaped bend. The drawback of this known embodiment resides in the fact that the hook-shaped bends protrude far out, the sinews and muscles are irritated and the bending of the leg is impeded in the area of the knee joint. Moreover, when using several bone nails, such as this is done as a rule, these hook-shaped bends impede one another. And finally, the hook-shaped bends, due to the elastic bone nails placed in the bone under tension, bear on a comparatively small site of the outer surface of the bone with considerable force, so that in particular in the case of older people with porous bones, there is the hazard of the bone caving in at this site.
It has been proposed to form the coupling part as a platelet-shaped flattening of the distal nail end. In this embodiment, the coupling part requires less space, the individual platelet-like flattenings can superimpose in the manner of roof tiles and do not hamper each other and the specific pressure per unit area is reduced by increasing the area, so that the hazard of the bone caving in in the area of the flat platelets abutting the outer surface of the bone is reduced, but not completely eliminated. Moreover, these platelets protruding from the impact hole also irritate the sinews and muscles running over this impact hole.
Further known is a bone nail of elastic material bent at least in its proximal end portion whose distal end portion has the same cross section as the entire nail and is provided with a flattening on at least one site of the nail periphery at a distance from the distal nail end, whereby this end area is formed as a coupling element permitting a non-rotatable connection to a tool serving for driving the nail. In this embodiment, the distal end area thus has no larger dimensions and still allows for the forming of a non-rotatable connection to the said tool for driving the nail. The distal nail ends can thus be accommodated in the guiding channel of a known insert member fixed in the impact hole of the bone whose guiding channel can have small dimensions because the distal end portions of the nails are not enlarged. An insert member of this type prevents the impact hole from splintering in the bone on driving the nail and thus becoming unintentionally enlarged and further permits the accommodation of the distal nail ends in the guiding channel so that they no longer protrude from the bone. This prevents an irritation of the muscles and sinews and the caving in of the bone in the area of the impact hole because the distal end of the nails formed as a coupling element no longer abuts the outer surface of the bone under tension, but instead the forces are taken up by the insert member and distributed by this evenly along the entire periphery of the impact hole to the bone.
In the known bone nails having at least one flattening at the distal nail end, the front faces via which the flattening merges with the circumference of the bone nail extend perpendicularly to the flattening. As a result, in this known embodiment, those parts of the tool cooperating with the flattening must be fixed by means of a sleeve in order to prevent slipping off from the flattening. This sleeve considerably increases the circumference of the tool in that area where the coupling of the same with the distal nail end formed as a coupling element takes place. When the distal nail ends are accommodated in the guiding channel of the said insert member having small dimensions, the coupling of the tool with the distal nail ends is difficult and sometimes impossible for lack of space. This constitutes a major disadvantage particularly when driving the nails back for removal from the medullary canal. For while the nail can be driven into the medullary canal during the last step of driving in which the distal nail ends enter the guiding channel by means of a tool which cooperates merely with the nail end on the front side, which no longer requires a coupling by means of the flattening, the driving back of the bone nails for removing them from the medullary canal demands a connection between the nail and the tool required for the driving back via the flattening.